The present invention relates to a telescopic pump.
Manual pumps are often used to inflate balls and tires. a conventional type of manual pump has a cylinder. The cylinder has a first end defining a nozzle and a second end defining an opening. A piston has a hub and first and second disks which are formed on the hub in a spaced manner. A plurality of holes are defined through the first disk of the piston. A sealing ring is mounted between the first and second disks of the piston. A limit defines a hub. A stem is inserted through the hub of the limit. The stem is further inserted through a spring. Then, a first end of the stem is attached in the hub of the piston. A second end of the stem is attached to a T-shaped handle. The piston is slidably received in the cylinder. The opening which is defined in the cylinder is limited by means of the limit. Grease is provided on the piston.
As the T-shaped handle is pulled, the piston is moved, by means of the stem, from the first end of the cylinder toward the second end of the cylinder. The sealing ring is thus pushed against the first disk of the piston. The grease provides a sealing effect between the cylinder and the sealing ring and a sealing effect between the sealing ring and the first disk of the piston. However, a gap is defined between the cylinder and the second disk of the piston. Thus, air is allowed to flow through the gap which is defined between the cylinder and the second disk of the piston and further through the holes which are defined through the first disk of the piston. As a result, air is drawn into the cylinder. In the above-mentioned stroke, the spring acts a buffer between the piston and the limit as the former is moved toward the latter. The limit will not be dislodged from the cylinder when the piston impacts against the limit via the spring.
As the handle is pushed, the piston is moved, by means of the stem, from the second end of the cylinder toward the first end of the cylinder. The sealing ring is thus pushed against the second disk of the piston. The grease provides a sealing effect between the cylinder and the sealing ring and a sealing effect between the sealing ring and the second disk of the piston. As air is kept from passing between the cylinder and the sealing ring and between the sealing ring and the second disk of the piston, air is pushed out of the cylinder through the nozzle which is defined through the cylinder.
Obviously, to pump a certain amount of air into a ball for example, fewer strokes of the piston in the cylinder are required if the cylinder is longer. The conflict between a desired greater length of a cylinder to reduce the frequency of strokes and the desired shorter length of a cylinder to achieved a compact size contributes to the inconvenience for a user of the pump. Therefore, there is a long and unfulfilled need for a convenient pump which saves the labor of its user and requires a small storage space.